They then proceeded to explore both the Red River and its western tributary the Assiniboin.

On the Assiniboin was afterwards built the post of Fort La Reine, and from this place in 1738 La Verendrye started with two of his sons, several other Frenchmen, a few Canadian voyageurs, and twenty-five Assiniboin Indians.

Leaving the Assiniboin River, they crossed the North Dakota prairies on foot.

Owing to the timidity of his Indian guides, La Verendrye was not led direct to the Missouri River, the "Great River of the West", but along a zigzag route which permitted his guides to reinforce their numbers at Assiniboin villages, and every now and then join in a bison hunt.

All the party were on foot, horses not then having reached the Assiniboin tribe.